Expandable structures for deployment in interior body regions

ABSTRACT

Apparatus for deploying an expandable structure in interior body regions provide an outer catheter tube, an inner catheter tube sized and configured to be received within the outer catheter tube, and an expandable structure having a distal end and a proximal end. The expandable structure also has a first end region adjacent the distal end and a second end region adjacent the proximal end. The distal end is bonded to the inner catheter tube to form a first bonded region and the proximal end is bonded to the outer catheter tube to form a second bonded region. The first end region is inverted to overlie the first bonded region and the second end region is inverted to overlie the second bonded region.

RELATED APPLICATIONS

[0001] This application is a divisional of copending U.S. patentapplication Ser. No. 09/918,942, filed Jul. 31, 2001, which is adivisional of U.S. patent application Ser. No. 09/404,662, filed Sep.23, 1999, now U.S. Pat. No. 6,280,456, which is a divisional of U.S.patent application Ser. No. 08/911,827, filed Aug. 15, 1997, now U.S.Pat. No. 5,972,015.

FIELD OF THE INVENTION

[0002] The invention relates to expandable structures, which, in use,are deployed in interior body regions of humans and other animals.

BACKGROUND OF THE INVENTION

[0003] The deployment of expandable structures into interior bodyregions is well known. For example, expandable structures, genericallycalled “balloons,” are deployed during angioplasty to open occludedblood vessels. As another example, U.S. Pat. Nos. 4,969,888 and5,108,404 disclose apparatus and methods the use of expandablestructures for the fixation of fractures or other osteoporotic andnon-osteoporotic conditions of human and animal bones.

[0004] Many interior regions of the body, such as the vasculature andinterior bone, possess complex, asymmetric geometries. Even if aninterior body region is somewhat more symmetric, it may still bedifficult to gain access along the natural axis of symmetry.

[0005] For example, deployment of an expandable structure in the regionof branched arteries or veins can place the axis of an expandablestructure off-alignment with the axis of the blood vessel which thestructure is intended to occupy. As another example, insertion of anexpandable structure into bone can require forming an access portal thatis not aligned with the natural symmetry of the bone. In theseinstances, expansion of the structure is not symmetric with respect tothe natural axis of the region targeted for treatment. As a result,expansion of the body is not symmetric with respect to the natural axisof the targeted region.

[0006] It can also be important to maximize the size and surface area ofan expandable structure when deployed in an interior body region.Current medical balloons manufactured by molding techniques are designedto be guided into a narrow channel, such as a blood vessel or thefallopian tube, where they are then inflated. In this environment, thediameter of the balloon is critical to its success, but the length isless so. Such balloons only need to be long enough to cross the area ofintended use, with few constraints past the effective portion of theinflated balloon. This allows conventional balloons to be constructed inthree molded pieces, comprising a cylindrical middle section and twoconical ends, bonded to a catheter shaft. As a practical matter, neitherthe length of the conical end, nor the length of the bond of the balloonto the catheter shaft, affect the function of conventional balloons, andthese regions on conventional balloons are often 1 cm in length or more.Indeed, the larger the balloon diameter, the longer the end cone, whichcreates a tradeoff between maximum effective length and maximumeffective diameter. This tradeoff makes optimization of conventionalstructures problematic in interior structures with defined lengths, suchas bone.

SUMMARY OF THE INVENTION

[0007] One aspect of the invention provides a device for deployment ininterior body regions. The device comprises an outer catheter tube, aninner catheter tube sized and configured to be received within the outercatheter tube, and an expandable structure having a distal end and aproximal end. The expandable structure also has a first end regionadjacent the distal end and a second end region adjacent the proximalend. The distal end is bonded to the inner catheter tube to form a firstbonded region and the proximal end is bonded to the outer catheter tubeto form a second bonded region. The first end region is inverted tooverlie the first bonded region and the second end region is inverted tooverlie the second bonded region. The inverted end regions provide amaximum diameter along essentially the entire length of the expandablestructure.

[0008] In a preferred embodiment, inversion of the proximal and distalend regions of the expandable structure create double-jointed endregions.

[0009] In one embodiment, the proximal and distal ends of the expandablestructure are bonded by an adhesive bonding process.

[0010] In another embodiment, the proximal and distal ends of theexpandable structure are bonded by a melt bonding process.

[0011] In one embodiment, no portion of the inner catheter tubeprotrudes beyond the expandable structure.

[0012] Another aspect of the invention provides a method formanufacturing a device for deployment in interior body regions. Themethod provides an outer catheter tube having a distal end and an innercatheter tube, the inner catheter tube being slidable within the outercatheter tube, and an expandable structure having a distal end, a firstend region adjacent the distal end, a proximal end, and a second endregion adjacent the proximal end. The inner catheter tube is insertedinto the outer catheter tube. The inner catheter tube is moved a firstdistance beyond the distal end of the outer catheter tube. The distalend of the expandable structure is bonded to the inner catheter tube toform a first bonded region and the proximal end of the expandablestructure is bonded to the outer catheter tube to form a second bondedregion. The inner catheter is moved a second distance beyond the distalend of the outer catheter tube, the second distance being a lesserdistance beyond the distal end of the outer catheter tube than the firstdistance to invert the first and second end regions such that the firstand second end regions overlie the first and second bonded regionsrespectively. The relative position of the inner catheter tube and theouter catheter tube are secured against further movement.

[0013] In one embodiment, the proximal and distal ends of the expandablestructure are bonded by an adhesive bonding process.

[0014] In another embodiment, the proximal and distal ends of theexpandable structure are bonded by a melt bonding process.

[0015] In one embodiment, the relative position of the inner cathetertube and the outer catheter tube are secured against further movement byan adhesive process.

[0016] Features and advantages of the inventions are set forth in thefollowing Description and Drawings, as well as in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a lateral view, partially broken away and in section, ofa lumbar vertebra taken generally along line 1-1 in FIG. 2;

[0018]FIG. 2 is a coronal view of the lumbar vertebra, partially cutaway and in section, shown in FIG. 1;

[0019]FIG. 3 is a top view of a probe including a catheter tube carryinga tubular expandable structure of conventional construction, shown in asubstantially collapsed condition;

[0020]FIG. 4 is an enlarged side view of the tubular expandablestructure carried by the probe shown in FIG. 3, shown in a substantiallyexpanded condition;

[0021]FIG. 5 is a lateral view of the lumbar vertebra shown in FIGS. 1and 2, partially cut away and in section, with the expandable structureshown in FIGS. 3 and 4 deployed by transpedicular access when in asubstantially collapsed condition;

[0022]FIG. 6 is a coronal view of the transpedicular access shown inFIG. 5, partially cut away and in section;

[0023]FIG. 7 is a lateral view of the transpedicular access shown inFIG. 5, with the expandable structure shown in FIGS. 3 and 4 in asubstantially expanded condition, forming a cavity that is not centeredwith respect to the middle region of the vertebral body;

[0024]FIG. 8 is a coronal view of the transpedicular access shown inFIG. 7, partially cut away and in section;

[0025]FIG. 9 is a coronal view of the lumbar vertebra shown in FIGS. 1and 2, partially cut away and in section, with the expandable structureshown in FIGS. 3 and 4 deployed by postero-lateral access when in asubstantially collapsed condition;

[0026]FIG. 10 is a coronal view of the postero-lateral access shown inFIG. 9, with the expandable structure shown in a substantially expandedcondition, forming a cavity that is not centered with respect to themiddle region of the vertebral body;

[0027]FIGS. 11A and 11B are side views of improved expandablestructures, each having an axis of expansion that is offset by an acuteangle and not aligned with the axis of the supporting catheter tube;

[0028]FIG. 12 is a lateral view of the lumbar vertebra shown in FIGS. 1and 2, partially cut away and in section, with the offset expandablestructure shown in FIG. 11A deployed by transpedicular access and beingin a substantially expanded condition, forming a cavity that issubstantially centered with respect to the middle region of thevertebral body;

[0029]FIG. 13 is a coronal view of the lumbar vertebra shown in FIGS. 1and 2, partially cut away and in section, with the offset expandablestructure shown in FIG. 11 deployed by postero-lateral access and beingin a substantially expanded condition, forming a cavity that issubstantially centered with respect to the middle region of thevertebral body;

[0030]FIGS. 14A and 14B are side views of other embodiments of improvedexpandable structures, each having an axis of expansion that is offsetby a distance from the axis of the supporting catheter tube;

[0031]FIG. 15 is a side view of a conventional expandable structureshown in FIG. 4, enlarged to show further details of its geometry whensubstantially expanded;

[0032]FIG. 16 is a side view of an improved expandable structure, whenin a substantially expanded condition, which includes end regions havingcompound curvatures that reduce the end region length and therebyprovide the capability of maximum bone compaction substantially alongthe entire length of the structure;

[0033]FIG. 17 is a side view of an improved expandable structure, whenin a substantially expanded condition, which includes end regions havingcompound curvatures that invert the end regions about the terminalregions, where the structure is bonded to the supporting catheter tube,to provide the capability of maximum bone compaction substantially alongthe entire length of the structure;

[0034]FIG. 18 is a side section view of an improved expandablestructure, when in a substantially expanded condition, which includesend regions that have been tucked or folded about the terminal regions,where the structure is bonded to the supporting catheter tube, toprovide the capability of maximum bone compaction substantially alongthe entire length of the structure;

[0035]FIG. 19 is a side section view of a tubular expandable structurehaving a distal end bonded to an inner catheter tube and a proximal endbonded to an outer catheter tube, the inner catheter tube being slidablewithin the outer catheter tube;

[0036]FIG. 20 is a side section view of the tubular expandable structureshown in FIG. 19, after sliding the inner catheter tube within the outercatheter tube to invert the end regions of the structure about thedistal and proximal bonds, to thereby provide the capability of maximumbone compaction substantially along the entire length of the structure;

[0037]FIG. 21 is a side section view of a tubular expandable structurehaving a distal end bonded to an inner catheter tube and a proximal endbonded to an outer catheter tube, the inner catheter tube and structurebeing made of a more compliant material than the outer catheter tube toprovide proportional length and diameter expansion characteristics;

[0038]FIG. 22 is an enlarged plan view of a branched blood vasculatureregion, in which an occlusion exists;

[0039]FIG. 23 is a further enlarged view of the branched bloodvasculature region shown in FIG. 22, in which an asymmetric expandablestructure of the type shown in FIG. 11 is deployed to open theocclusion;

[0040]FIG. 24 is a plan view of a sterile kit to store a single useprobe, which carries an expandable structures as previously shown;

[0041]FIG. 25 is an exploded perspective view of the sterile kit shownin FIG. 24;

[0042]FIG. 26 is a side view, with parts broken away and in section, ofan expandable structure having an enclosed stiffening member, tostraighten the structure during passage through a guide sheath into aninterior body region; and

[0043]FIG. 27 is a side view of the expandable structure shown in FIG.27, after deployment beyond the guide sheath and into the interior bodyregion, in which the stiffening member includes a distal region having apreformed bend, which deflects the structure relative to the axis of theguide sheath.

[0044] The invention may be embodied in several forms without departingfrom its spirit or essential characteristics. The scope of the inventionis defined in the appended claims, rather than in the specificdescription preceding them. All embodiments that fall within the meaningand range of equivalency of the claims are therefore intended to beembraced by the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The preferred embodiment first describes improved systems andmethods that embody features of the invention in the context of treatingbones. This is because the new systems and methods are advantageous whenused for this purpose.

[0046] Another preferred embodiment describes the improved systems andmethods in the context of relieving constrictions or blockages withinbranched blood vessels. This is because the vasculature also presents anenvironment well suited to receive the benefits of the invention.

[0047] The two environments are described for the purpose ofillustration. However, it should be appreciated that the systems andmethods as described are not limited to use in the treatment of bones orthe vasculature. The systems and methods embodying the invention can beused virtually in any interior body region that presents an asymmetricgeometry, or otherwise requires an access path that is not aligned withthe natural axis of the region.

[0048] I. Deployment in Bones

[0049] The new systems and methods will be first described in thecontext of the treatment of human vertebra. Of course, other human oranimal bone types, e.g., long bones, can be treated in the same orequivalent fashion.

[0050]FIG. 1 shows a lateral (side) view of a human lumbar vertebra 12.FIG. 2 shows a coronal (top) view of the vertebra. The vertebra 12includes a vertebral body 26, which extends on the anterior (i.e., frontor chest) side of the vertebra 12. The vertebral body 26 is in the shapeof an oval disk. The geometry of the vertebral body 26 is generallysymmetric arranged about its natural mid-anterior-posterior axis 66,natural mid-lateral axis 67, and natural mid-top-to-bottom axis 69. Theaxes 66, 67, and 69 intersect in the middle region or geometric centerof the body 26, which is designated MR in the drawings.

[0051] As FIGS. 1 and 2 show, the vertebral body 26 includes an exteriorformed from compact cortical bone 28. The cortical bone 28 encloses aninterior volume 30 of reticulated cancellous, or spongy, bone 32 (alsocalled medullary bone or trabecular bone).

[0052] The spinal canal 36 (see FIG. 2), is located on the posterior(i.e., back) side of each vertebra 12. The spinal cord (not shown)passes through the spinal canal 36. The vertebral arch 40 surrounds thespinal canal 36. Left and right pedicles 42 of the vertebral arch 40adjoin the vertebral body 26. The spinous process 44 extends from theposterior of the vertebral arch 40, as do the left and right transverseprocesses 46.

[0053] U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose apparatus andmethods for the fixation of fractures or other conditions of human andother animal bone systems, both osteoporotic and non-osteoporotic. Theapparatus and methods employ an expandable structure to compresscancellous bone and provide an interior cavity. The cavity receives afilling material, e.g., bone cement, which hardens and provides renewedinterior structural support for cortical bone. The compaction ofcancellous bone also exerts interior force upon cortical bone, making itpossible to elevate or push broken and compressed bone back to or nearits original prefracture, or other desired, condition.

[0054]FIG. 3 shows a tool 48, which includes a catheter tube 50 having aproximal and a distal end, respectively 52 and 54. The catheter tube 50includes a handle 51 to facilitate gripping and maneuvering the tube 50.The handle 51 is preferably made of a foam material secured about thecatheter tube 50.

[0055] The distal end 54 carries an expandable structure 56, which FIG.3 shows to be of conventional construction. The structure 56 is shown inFIG. 3 in a substantially collapsed geometry. The structure 56conventionally comprises an elongated tube, formed, for example, bystandard polymer extrusion and molding processes. The tubular structure56 is bonded at its opposite ends 58 to the catheter tube 50, using, forexample, an adhesive. When substantially collapsed, the structure 56 canbe inserted into an interior body region.

[0056] Tubular bodies of the type shown in FIG. 3 are made from polymermaterials and are commonly deployed in veins and arteries, e.g., inangioplasty applications. FIG. 4 shows an enlarged view of the structure56 when in a substantially expanded geometry. As FIG. 4 shows, themiddle region 64 of the tubular structure 56, when substantiallyexpanded, assumes a generally cylindrical shape, which is symmetricabout the main axis 60 of the catheter tube 50. Expansion stretches thepolymer material of the structure 56 near its bonded ends 58 to formgenerally conical end portions 62.

[0057] The structure 56 can be inserted into bone in accordance with theteachings of the above described U.S. Pat. Nos. 4,969,888 and 5,108,404.For a vertebral body 26, access into the interior volume 30 can beaccomplished, for example, by drilling an access portal 43 througheither pedicle 42. This is called a transpedicular approach, which FIG.5 shows in lateral view and FIG. 6 shows in coronal view. As FIG. 5shows, the access portal 43 for a transpedicular approach enters at thetop of the vertebral body 26, where the pedicle 42 is relatively thin,and extends at an angle downward toward the bottom of the vertebral body26 to enter the interior volume 30. As FIGS. 5 and 6 show, in a typicaltranspedicular approach, the access portal 43 aligns the catheter tubeaxis 60 obliquely with respect to all natural axes 66, 67, or 69 of thevertebral body 26.

[0058] As the conventional structure 56 expands within the interiorvolume 30 (as FIGS. 7 and 8 show, respectively, in lateral and coronalviews for the transpedicular approach), the structure 56 symmetricallyexpands about the catheter tube axis 60, compressing cancellous bone 32to form a cavity 68. However, since the catheter tube axis 60 isoriented obliquely relative to all natural axes 66, 67, or 69, theformed cavity is not centered with respect to the middle region MR.Instead, the cavity 68 is offset on one lateral side of the middleregion MR (as FIG. 8 shows) and also extends from top to bottom atoblique angle through the middle region MR (as FIG. 7 shows).

[0059] Due to these asymmetries, the cavity 68 will not provide optimalsupport to the middle region MR when filled with bone cement. Since thebone cement volume is not centered about the middle region MR, thecapability of the vertebral body 26 to withstand loads is diminished.The asymmetric compaction of cancellous bone 32 in the interior volume30 may also exert unequal or nonuniform interior forces upon corticalbone 32, making it difficult to elevate or push broken and compressedbone.

[0060] As FIG. 9 shows, access to the interior volume 30 of thevertebral body 26 also can be achieved by drilling an access portal 45through a side of the vertebral body 26, which is called apostero-lateral approach. The portal 45 for the postero-lateral approachenters at a posterior side of the body 26 and extends at angle forwardlytoward the anterior of the body 26.

[0061] As FIG. 9 shows, the orientation of the portal 45 in a typicalpostero-lateral approach does not permit parallel or perpendicularalignment of the catheter tube axis 60 with either the mid-lateral axis67 or the mid-anterior-posterior axis 66 of the vertebral body 26. As aresult, symmetric expansion of the conventional structure 56 about thecatheter tube axis 60 forms an off-centered cavity 68′, which extendsobliquely across the middle region MR of the body 26, as FIG. 10 viewshows. As with the cavity 68 formed by the structure 56 usingtranspedicular access, the off-centered cavity 68′ formed by thestructure 56 using postero-lateral access also fails to provide optimalsupport to the middle region MR when filled with bone cement.

[0062] A. Optimal Orientation for Cancellous Bone Compaction

[0063]FIG. 11A shows an improved bone treating tool 14, which includes acatheter tube 16 carrying at its distal end 18 an expandable structure20. The catheter tube 16 can, at its proximal end, be configured likethe tube 50 shown in FIG. 3, with a handle 51 made of, e.g., a foammaterial.

[0064]FIG. 11A shows the structure 20 in a substantially expandedcondition, in which the structure comprises a cylinder 21 with generallyconical portions 34, each having a top 25 and a base 27. The tops 25 ofconical portions 34 are secured about the catheter tube 16 and, in thisrespect, are generally aligned with the catheter tube axis 24. However,unlike the expandable structure 56 shown in FIG. 4, the main axis 22 ofthe cylinder 21 and the axis 24 of the catheter tube 16 are not aligned.Instead, the cylinder axis 22 is offset at an angle A from the cathetertube axis 24. As a result, the structure 20, when substantially expanded(as FIG. 11A shows), is not symmetric with respect to the catheter tubeaxis 24.

[0065] In FIG. 11A, the bases 27 of the conical portions 34 extendgenerally perpendicularly to the cylinder axis 22. In this orientation,the tops 25 and the bases 27 are not parallel to each other. Otherorientations are possible. For example, in FIG. 11B, the bases 27 of theconical portions 34 extend generally perpendicularly to the cathetertube axis 24. In this orientation, the tops 25 and the bases 27 aregenerally parallel to each other.

[0066]FIG. 12 shows in lateral view, the offset structure 20 shown inFIG. 11A deployed by a transpedicular approach in the interior volume 30of a vertebral body 26. As before shown in FIGS. 7 and 8, thetranspedicular approach in FIG. 12 does not align the catheter tube axis24 with any of the natural axes 66, 67, and 69 of the body 26. However,as FIG. 12 shows, the expansion of the offset cylinder 21 of thestructure 20 about its axis 22 is not symmetric with respect to thecatheter tube axis 24. Instead, expansion of the offset structure 20 isgenerally aligned with the natural axes 66 and 69 of the vertebral body26. As FIG. 12 shows, a single offset structure 20 introduced bytranspedicular access, forms a cavity 38 that, while still laterallyoffset to one side of the middle region MR (as shown in FIG. 8), isnevertheless symmetric in a top-to-bottom respect with the middle regionMR. A matching, adjacent cavity can be formed by transpediculardeployment of a second offset structure 20 on the opposite lateral sideof the vertebral body 26. The composite cavity, formed by the two offsetbodies 20, introduced simultaneously or in succession by dualtranspedicular access, is substantially centered in all respects aboutthe middle region MR.

[0067]FIG. 13 shows the offset expandable structure 20 deployed by apostero-lateral approach in the interior volume 30 of a vertebral body26. As before shown in FIG. 9, the postero-lateral approach in FIG. 13does not align the catheter tube axis 24 with the natural axes 66 and 67of the body 26. The expansion of the offset structure 20, which isasymmetric about the catheter tube axis 24, is nevertheless generallysymmetric with respect to all natural axes 66, 67, and 69 of thevertebral body 26. A single offset structure 20, deployed bypostero-lateral access, forms a cavity 38′, which is substantiallycentered about the middle region MR.

[0068] A cavity centered with respect to the middle region MR providessupport uniformly across the middle region MR when filled with bonecement. The capability of the vertebral body 26 to withstand loads isthereby enhanced. The symmetric compaction of cancellous bone 32 in theinterior volume 30 that a centered cavity provides also exerts moreequal and uniform interior forces upon cortical bone 32, to elevate orpush broken and compressed bone.

[0069]FIGS. 14A and 14B show an expandable structure 200 having anoffset, asymmetric geometry different than the geometry of the offsetexpandable structure 20 shown in FIGS. 11A and 11B. In FIGS. 11A and11B, the offset angle A between the cylinder axis 22 and the cathetertube axis 24 is an acute angle. As a result, the axis 22 of thestructure 20 is offset in a nonparallel dimension or plane relative tothe catheter tube axis 24. In FIGS. 14A and 14B, the offset angle Abetween the cylinder axis 220 and the catheter tube axis 240 is zero, asthe axis 220 of the cylinder 210 is offset at a distance from and in agenerally parallel dimension or plane relative to the catheter tube axis240. The catheter tube 160 can, at its proximal end, be configured likethe tube 50 shown in FIG. 3, with a handle 51 made of, e.g., a foammaterial.

[0070] As in FIGS. 11A and 11B, the tops 250 of conical portions 340 aresecured about the catheter tube 160 and, in this respect, are generallyaligned with the catheter tube axis 240. In FIGS. 14A and 14B, theorientation of the bases 270 of the conical portions 340 differ. In FIG.14A, the bases 270 of the conical portions 340 extend generallyperpendicularly to the catheter tube axis 240, and are thereforegenerally parallel to the tops 250 (comparable to the orientation shownin FIG. 11B). In FIG. 14B, the bases 270 of the conical portions 340extend at an angle B to the catheter tube axis 240. In this orientation,the tops 250 and the bases 270 are not parallel to each other.

[0071]FIGS. 11A and 11B and 14A and 14B show that it is possible, byadjustment of the offset angle A, as well as adjustment of theorientation of the conical end bases, to achieve virtually any desiredoffset geometry, and thereby tailor the orientation of the expandablestructure to the particular geometry of the point of use.

[0072] B. Maximizing Cancellous Bone Compaction

[0073] Referring back to FIG. 4, when the conventional tubular structure56 shown in FIG. 4 is substantially expanded, material of the structureis stretched into conical sections 62 near the ends 58, which are bondedto the catheter tube 50. FIG. 15 shows the geometry of expanded tubularstructure 56 in greater detail. The conical portions 62 extend at a coneangle α from the bonded ends 58. The expanded structure 56 thereforepresents the generally cylindrical middle region 64, where the maximumdiameter of the structure 56 (BODY_(DIA)) exists, and the conicalportions 62, which comprise regions of diameter that decreases withdistance from the middle region 64 until reaching the diameter of thecatheter tube (TUBE_(DIA)).

[0074] Due to the geometry shown in FIG. 15, maximum cancellous bonecompaction does not occur along the entire length (L2) of theconventional structure 56, as measured between the bonded ends 58.Instead, maximum cancellous bone compaction occurs only along theeffective length (L1) of the cylindrical middle region 64 of thestructure 56, where the structure 56 presents its maximum diameterBODY_(DIA). Cancellous bone compaction diminishes along the length ofthe conical portions 62, where the structure's diameter progressivelydiminishes. At the bonded ends 58, and portions of the catheter tube 50extending beyond the bonded ends 58, no bone compaction occurs. Thecatheter tube 50 can, at its proximal end, be configured like the tube50 shown in FIG. 3, with a handle 51 made of, e.g., a foam material.

[0075] The lengths (Lc) of the conical regions 62 and bonded ends 58relative to the entire length of the structure 56 (L2) are importantindications of the overall effectiveness of the structure 56 forcompacting cancellous bone. The effective bone compaction length (L1) ofany expandable structure having conical end regions, such as structure56 shown in FIG. 15, can be expressed as follows:

L1=L2−2(Lc)

[0076] where the length of a given conical region (Lc) can be expressedas follows: ${Lc} = \frac{h}{\tan \frac{\alpha}{2}}$ where:$h = \frac{{BODY}_{DIA} - {TUBE}_{DIA}}{2}$

[0077] where (see FIG. 15):

[0078] BODY_(DIA) is the maximum diameter of the middle region 64, whensubstantially expanded,

[0079] TUBE_(DIA) is the diameter of the catheter tube 50, and

[0080] α is the angle of the conical portion.

[0081] As the foregoing expressions demonstrate, for a given conicalangle α, the length Lc of the conical portions 62 will increase withincreasing maximum diameter BODY_(DIA) of the middle region 64. Thus, asBODY_(DIA) is increased, to maximize the diameter of the formed cavity,the lengths Lc of the conical portions 62 also increase, therebyreducing the effective length L₁ of maximum cancellous bone compaction.

[0082] The bone compaction effectiveness of an expandable structure of agiven maximum diameter increases as L1 and L2 become more equal. Thegeometry of a conventional tubular structure 56 shown in FIG. 15 poses atradeoff between maximum compaction diameter and effective compactionlength. This inherent tradeoff makes optimization of the structure 56for bone compaction application difficult.

[0083]FIG. 16 shows an improved structure 70 having a geometry, whensubstantially expanded, which mitigates the tradeoff between maximumcompaction diameter and effective compaction length. The structure 70includes a middle region 72, where BODY_(DIA) occurs. The structure 70also includes end regions 74, which extend from the middle region 72 tothe regions 76, where the material of the structure is bonded to thecatheter tube 78, at TUBE_(DIA). The catheter tube 78 can, at itsproximal end, be configured like the tube 50 shown in FIG. 3, with ahandle 51 made of, e.g., a foam material.

[0084] In the embodiment shown in FIG. 16, the end regions 74 are moldedor stressed to provide a non-conical diameter transformation betweenBODY_(DIA) and TUBE_(DIA). The diameter changes over two predefinedradial sections r1 and r2, forming a compound curve in the end regions74, instead of a cone. The non-conical diameter transformation of radialsections r1 and r2 between BODY_(DIA) and TUBE_(DIA) reduces thedifferential between the effective bone compaction length L1 of thestructure 70 and the overall length L2 of the structure 70, measuredbetween the bond regions 76.

[0085]FIG. 17 shows another improved expandable structure 80 having ageometry mitigating the tradeoff between maximum compaction diameter andeffective compaction length. Like the structure 70 shown in FIG. 16, thestructure 80 in FIG. 16 includes a middle region 82 of BODY_(DIA) andend regions 84 extending from the middle region to the bonded regions86, at TUBE_(DIA). As the structure 70 in FIG. 16, the end regions 84 ofthe structure 80 make a non-conical diameter transformation betweenBODY_(DIA) and TUBE_(DIA). In FIG. 17, the predefined radial sections r1 and r 2 are each reduced, compared to the radial section r1 and r2 inFIG. 16. As a result, the end regions 84 take on an inverted profile. Asa result, the entire length L2 between the bonded regions 86 becomesactually less than the effective length L1 of maximum diameterBODY_(DIA). The catheter tube can, at its proximal end, be configuredlike the tube 50 shown in FIG. 3, with a handle 51 made of, e.g., a foammaterial.

[0086] The structures 70 and 80, shown in FIGS. 16 and 17, whensubstantially inflated, present, for a given overall length L2, regionsof increasingly greater proportional length L1, where maximum cancellousbone compaction occurs.

[0087] Furthermore, as in FIG. 17, the end regions 84 are inverted aboutthe bonded regions 86. Due to this inversion, bone compaction occurs incancellous bone surrounding the bonded regions 86. Inversion of the endregions 84 about the bonded regions 86 therefore makes it possible tocompact cancellous bone along the entire length of the expandablestructure 80.

[0088]FIG. 18 shows another embodiment of an improved expandablestructure 90. Like the structure 80 shown in FIG. 17, the structure 90includes a middle region 92 and fully inverted end regions 94 overlyingthe bond regions 96. The structure 80 comprises, when substantiallycollapsed, a simple tube. At least the distal end of the tubularstructure 80 is mechanically tucked or folded inward and placed intocontact with the catheter tube 98. As shown in FIG. 18, both proximaland distal ends of the tubular structure are folded over and placed intocontact with the catheter tube 98. The catheter tube 98 can, at itsproximal end, be configured like the tube 50 shown in FIG. 3, with ahandle 51 made of, e.g., a foam material.

[0089] The catheter tube 98 is dipped or sprayed beforehand with amaterial 102 that absorbs the selected welding energy, for example,laser energy. The folded-over ends 94 are brought into abutment againstthe material 102. The welding energy transmitted from an external sourcethrough the middle region 92 is absorbed by the material 102. A weldforms, joining the material 102, the folded-over ends 94, and thecatheter tube 50. The weld constitutes the bond regions 96.

[0090] The inverted end regions 94 of the structure 90 achieve an abrupttermination of the structure 90 adjacent the distal end 104 of thecatheter tube 98, such that the end regions 94 and the distal cathetertube end 104 are coterminous. The structure 90 possesses a region ofmaximum structure diameter, for maximum cancellous bone compaction,essentially along its entire length. The structure 90 presents noportion along its length where bone compaction is substantially lessenedor no cancellous bone compaction occurs.

[0091]FIGS. 19 and 20 show another embodiment of an expandable structure110. As FIG. 20 shows, the structure 110 includes a middle region 112 ofmaximum diameter BODY_(DIA) and inverted end regions 114, which overliethe bonded regions 116.

[0092]FIG. 19 shows the structure 110 before the end regions 114 havebeen inverted in the manufacturing process. As FIG. 19 shows, thestructure 110 comprises, when substantially collapsed, a simple tube. Tofacilitate formation of the inverted end regions 114 and bonded regions116, a two-piece catheter tube is provided, comprising an outer cathetertube 118 and an inner catheter tube 120. The inner catheter tube 120slides within the outer catheter tube 118. The catheter tube 118 can, atits proximal end, be configured like the tube 50 shown in FIG. 3, with ahandle 51 made of, e.g., a foam material.

[0093] As FIG. 19 shows, during the manufacturing process, the innercatheter tube 120 is moved a first distance d1 beyond the outer cathetertube 118. In this condition, the proximal and distal ends 122 and 124 ofthe tubular structure 110 are bonded, without folding over or tuckingin, about the inner catheter tube 118 and the outer catheter tube 120,respectively. The unfolded ends 122 and 124 of the tubular structure 110can then be directly exposed to conventional adhesive or melt bondingprocesses, to form the bonded regions 116.

[0094] Once the bonded regions 116 are formed, the inner catheter tube120 is moved (see arrow 130 in FIG. 20) to a distance d2 (shorter thand1) from the end of the outer catheter tube 118. The shortening of theinner tube 120 relative to the outer tube 120 inverts the ends 122 and124. The inversion creates double jointed end regions 116 shown in FIG.20, which overlie the bonded regions 116. The relative position of theouter and inner catheter tubes 118 and 120 shown in FIG. 20 is securedagainst further movement, e.g., by adhesive, completing the assemblageof the structure 110.

[0095] The double jointed inverted ends 114 of the structure 110 in FIG.20, like single jointed inverted ends 94 of the structure 90 in FIG. 18,assure that no portion of the catheter tube protrudes beyond theexpandable structure. Thus, there is no region along either structure 94or 114 where cancellous bone compaction does not occur. Like thestructure 90 shown in FIG. 18, the structure 110 in FIG. 20 presents amaximum diameter for maximum cancellous bone compaction essentiallyalong its entire length.

[0096]FIG. 21 shows another embodiment of an improved expandablestructure 300 well suited for deployment in an interior body region.Like the structure 110 shown in FIGS. 19 and 20, the structure 300 inFIG. 21 includes an inner catheter tube 304 secured within an outercatheter tube 302. Like the structure 110 shown in FIGS. 19 and 20, thedistal end 310 of the inner catheter tube 304 in FIG. 21 extends beyondthe distal end 308 of the outer catheter tube 302.

[0097] The outer diameter of the inner catheter tube 304 is likewisesmaller than the inner diameter of the outer catheter tube 302. A flowpassage 312 is defined by the space between the two catheter tubes 302and 304.

[0098] The proximal end 314 of an expandable body 306 is bonded to thedistal end 308 of the outer catheter tube 302. The distal end 316 of theexpandable body 306 is bonded to the distal end 310 of the innercatheter tube 304. An inflation medium 318 is conveyed into the body 306through the flow passage 312, causing expansion of the body 306.

[0099] In FIG. 21, the physical properties of the structure 300 at theproximal body end 314 differ from the physical properties of thestructure 300 at the distal body end 316. The different physicalproperties are created by material selection. More particularly,materials selected for the inner catheter tube 304 and the expandablebody 306 are more compliant (i.e., more elastic) than the materialsselected for the outer catheter tube 302. In a preferred embodiment,materials selected for the expandable body 306 and the inner cathetertube 304 possess hardness properties of less than about 90 Shore A andultimate elongation of greater than about 450%, e.g., more compliantpolyurethanes. In a preferred embodiment, materials selected for theouter catheter tube 302 possess hardness properties of greater thanabout 45 Shore D and ultimate elongation of less than about 450%, e.g.,less compliant polyurethanes or polyethylenes.

[0100] Due to the differential selection of materials, the lack ofcompliance of the outer catheter tube 302 at the proximal body end 314is counterpoised during expansion of the body 306 against the complianceof the inner catheter tube 304 at the distal body end 316. The differentcompliance characteristics causes the body 306, during expansion, toincrease in length in proportion to its increase in diameter duringexpansion. By virtue of the more compliant body 306 and inner cathetertube 304, the structure 300 shown in FIG. 21 is elastic enough toconform to an interior body region, like inside a bone. Nevertheless,the structure 300 is constrained from over-expansion by attachment ofthe proximal end 314 of the body 306 to the less elastic outer cathetertube 302.

[0101] The bond between a given expandable structure and its associatedcatheter tube can be strengthened by using a CO2 or NdYAG laser to weldthe structure and tube materials together. Factors influencing jointstrength include energy wave length, energy pulse width, pulse period,head voltage, spot size, rate of rotation, working distance, angle ofattack, and material selection.

[0102] The catheter tube 302 can, at its proximal end, be configuredlike the tube 50 shown in FIG. 3, with a handle 51 made of, e.g., a foammaterial.

[0103] II. Deployment in the Vasculature

[0104]FIG. 22 shows a blood vasculature region 400. The region 400includes a first blood vessel 402, which extends along a first axis 404.The region 400 also includes a second blood vessel 406, which branchesfrom the first blood vessel 402 along a second axis 408 offset from thefirst axis 404.

[0105]FIG. 22 also shows the presence of an occlusion 410 adjacent thesecond blood vessel 406. The occlusion 410 can comprise, e.g., plaquebuildup along the interior wall of the second blood vessel 406.

[0106]FIG. 23 shows the distal end of a tool 412, which has beenintroduced into the vascular region 400 for the purpose of opening theocclusion 410. The tool 412 comprises a catheter tube 416, which carriesat its distal end an expandable structure 420 of the type shown in FIG.11. The catheter tube 416 can, at its proximal end, be configured likethe tube 50 shown in FIG. 3, with a handle 51 made of, e.g., a foammaterial.

[0107] The catheter tube 416 is introduced by conventional vascularintroducer and, with fluoroscopic monitoring, steered to the targetedregion 400 along a guidewire 430 deployed within the first and secondvessels 402 and 406. The structure 420 is expanded using a sterilefluid, like saline or a radio-contrast medium. FIG. 23 shows thestructure 420 in a substantially expanded condition.

[0108] Like the expandable structure 20 shown in FIG. 11, the main axis422 of the structure 420 shown in FIG. 23 and the axis 424 of thecatheter tube 416 are not aligned. Instead, the structure axis 422 isoffset at a selected acute angle A from the catheter tube axis 424. Dueto the offset angle A, the structure 420, when substantially expanded(as FIG. 23 shows), is not symmetric with respect to the catheter tubeaxis 424.

[0109] As FIG. 23 shows, the asymmetric expansion of the structure 420allows the physician to maintain the catheter tube 416 in axialalignment with the first blood vessel 402, while maintaining theexpandable structure 420 in axial alignment with the second blood vessel406. In this orientation, expansion of the structure 420 within thesecond blood vessel 406 opens the occlusion 410. The asymmetry of thestructure 420 relative to the catheter tube 416 thereby permits accessto branched blood vessels without complex manipulation and steering.

[0110] III. Deflection of the Structure

[0111] In all of the foregoing embodiments, a length of the associatedcatheter tube extends within the expandable structure. In theembodiments shown in FIGS. 4, 11A/B, 14A/B, and 15 to 18, the enclosedcatheter tube comprises an extension of the main catheter tube. In theembodiments shown in FIGS. 19 to 21, the enclosed catheter tubecomprises a separate catheter tube carried by the main catheter tube.

[0112] Regardless of the particular construction (see FIG. 26), theenclosed length of catheter tube 600 provides an interior lumen 602passing within the expandable structure 604. The lumen 602 accommodatesthe passage of a stiffening member or stylet 606 made, e.g., fromstainless steel or molded plastic material.

[0113] The presence of the stylet 606 serves to keep the structure 604in the desired distally straightened condition during passage through anassociated guide sheath 608 toward the targeted body region 610, as FIG.26 shows. Access to the target body region 610 through the guide sheath608 can be accomplished using a closed, minimally invasive procedure orwith an open procedure.

[0114] As shown in FIG. 27, the stylet 606 can have a preformed memory,to normally bend the distal region 612 of the stylet 606. The memory isovercome to straighten the stylet 606 when confined within the guidesheath 608, as FIG. 26 shows. However, as the structure 604 and stylet606 advance free of the guide sheath 608 and pass into the targetedregion 610, the preformed memory bends the distal stylet region 612. Thebend of the distal stylet region 612 bends the tube 600 and therebyshifts the axis 614 of the attached expandable structure 604 relative tothe axis 616 of the access path (i.e., the guide sheath 608). Theprebent stylet 606, positioned within the interior of the structure 604,further aids in altering the geometry of the structure 604 in accordancewith the orientation desired when the structure 604 is deployed for usein the targeted region 610.

[0115] IV. Material Selection

[0116] In any of the foregoing embodiments, the material of theexpandable structure can be selected according to the therapeuticobjectives surrounding its use. For example, materials including vinyl,nylon, polyethylenes, ionomer, polyurethane, and polyethylenetetraphthalate (PET) can be used. The thickness of the structure istypically in the range of {fraction (2/1000)}ths to {fraction(25/1000)}ths of an inch, or other thicknesses that can withstandpressures of up to, for example, 250-500 psi.

[0117] If desired, the material for the structure can be selected toexhibit generally elastic properties, like latex. Alternatively, thematerial can be selected to exhibit less elastic properties, likesilicone. Using expandable bodies with generally elastic or generallysemi-elastic properties, the physician monitors the expansion to assurethat over-expansion and wall failure do not occur. Furthermore,expandable bodies with generally elastic or generally semi-elasticproperties may require some form of external or internal restraints toassure proper deployment in bone. The use of internal or externalrestraints in association with expandable bodies used to treat bone isdiscussed in greater detail in copending U.S. patent application Ser.No. 08/485,394, filed Jun. 7, 1995, which is incorporated herein byreference.

[0118] Generally speaking, for use in treating bone, providingrelatively inelastic properties for the expandable structure, while notalways required, is nevertheless preferred, when maintaining a desiredshape and size within the bone is important, for example, in a vertebralbody, where the spinal cord is nearby. Using relatively inelasticbodies, the shape and size can be better predefined, taking into accountthe normal dimensions of the outside edge of the cancellous bone. Use ofrelatively inelastic materials also more readily permits the applicationof pressures equally in a defined geometry to compress cancellous bone.

[0119] When treating bone, the choice of the shape and size of aexpandable structure takes into account the morphology and geometry ofthe site to be treated. The shape of the cancellous bone to becompressed, and the local structures that could be harmed if bone weremoved inappropriately, are generally understood by medical professionalsusing textbooks of human skeletal anatomy along with their knowledge ofthe site and its disease or injury. The physician is also able to selectthe materials and geometry desired for the structure based upon prioranalysis of the morphology of the targeted bone using, for example,plain films, spinous process percussion, or MRI or CRT scanning. Thematerials and geometry of the structure are selected to optimize theformation of a cavity that, when filled with bone cement, providesupport across the middle region of the bone being treated.

[0120] In some instances, it is desirable, when creating a cavity, toalso move or displace the cortical bone to achieve the desiredtherapeutic result. Such movement is not per se harmful, as that term isused in this Specification, because it is indicated to achieve thedesired therapeutic result. By definition, harm results when expansionof the structure results in a worsening of the overall condition of thebone and surrounding anatomic structures, for example, by injury tosurrounding tissue or causing a permanent adverse change in bonebiomechanics.

[0121] As one general guideline, the selection of the geometry of theexpandable structure should take into account that at least 40% of thecancellous bone volume needs to be compacted in cases where the bonedisease causing fracture (or the risk of fracture) is the loss ofcancellous bone mass (as in osteoporosis). The preferred range is about30% to 90% of the cancellous bone volume. Compacting less of thecancellous bone volume can leave too much of the diseased cancellousbone at the treated site. The diseased cancellous bone remains weak andcan later collapse, causing fracture, despite treatment.

[0122] Another general guideline for the selection of the geometry ofthe expandable structure is the amount that the targeted fractured boneregion has been displaced or depressed. The expansion of the structurewithin the cancellous bone region inside a bone can elevate or push thefractured cortical wall back to or near its anatomic position occupiedbefore fracture occurred.

[0123] However, there are times when a lesser amount of cancellous bonecompaction is indicated. For example, when the bone disease beingtreated is localized, such as in avascular necrosis, or where local lossof blood supply is killing bone in a limited area, the expandablestructure can compact a smaller volume of total bone. This is becausethe diseased area requiring treatment is smaller.

[0124] Another exception lies in the use of an expandable structure toimprove insertion of solid materials in defined shapes, likehydroxyapatite and components in total joint replacement. In thesecases, the structure shape and size is defined by the shape and size ofthe material being inserted.

[0125] Yet another exception lays the use of expandable bodies in bonesto create cavities to aid in the delivery of therapeutic substances, asdisclosed in copending U.S. patent application Ser. No. 08/485,394,previously mentioned. In this case, the cancellous bone may or may notbe diseased or adversely affected. Healthy cancellous bone can besacrificed by significant compaction to improve the delivery of a drugor growth factor which has an important therapeutic purpose. In thisapplication, the size of the expandable structure is chosen by thedesired amount of therapeutic substance sought to be delivered. In thiscase, the bone with the drug inside is supported while the drug works,and the bone heals through exterior casting or current interior orexterior fixation devices.

[0126] The materials for the catheter tube are selected to facilitateadvancement of the expandable structure into cancellous bone. Thecatheter tube can be constructed, for example, using standard flexible,medical grade plastic materials, like vinyl, nylon, polyethylenes,ionomer, polyurethane, and polyethylene tetraphthalate (PET). Thecatheter tube can also include more rigid materials to impart greaterstiffness and thereby aid in its manipulation. More rigid materials thatcan be used for this purpose include stainless steel, nickel-titaniumalloys (Nitinol™ material), and other metal alloys.

[0127] V. Single Use

[0128] Expansion of any one of the expandable structures describedherein during first use in a targeted body region generates stress onthe material or materials which make up the structure. The materialstress created by operational loads during first use in a targeted bodyregion can significantly alter the molded morphology of the structure,making future performance of the structure unpredictable.

[0129] For example, expansion within bone during a single use createscontact with surrounding cortical and cancellous bone. This contact candamage the structure, creating localized regions of weakness, which mayescape detection. The existence of localized regions of weakness canunpredictably cause overall structural failure during a subsequent use.

[0130] In addition, exposure to blood and tissue during a single use canentrap biological components on or within the structure or theassociated catheter tube. Despite cleaning and subsequent sterilization,the presence of entrapped biological components can lead to unacceptablepyrogenic reactions.

[0131] As a result, following first use, the structure can not be reliedupon to reach its desired configuration during subsequent use and maynot otherwise meet established performance and sterilizationspecifications. The effects of material stress and damage caused duringa single use, coupled with the possibility of pyrogen reactions evenafter resterilization, reasonably justify imposing a single userestriction upon devices which carry these expandable structures fordeployment in bone.

[0132] To protect patients from the potential adverse consequencesoccasioned by multiple use, which include disease transmission, ormaterial stress and instability, or decreased or unpredictableperformance, the invention also provides a kit 500 (see FIGS. 24 and 25)for storing a single use probe 502, which carries an expandablestructure 504 described herein prior to deployment in bone.

[0133] In the illustrated embodiment (see FIGS. 24 and 25), the kit 500includes an interior tray 508. The tray 508 holds the probe 502 in alay-flat, straightened condition during sterilization and storage priorto its first use. The tray 508 can be formed from die cut cardboard orthermoformed plastic material. The tray 508 includes one or more spacedapart tabs 510, which hold the catheter tube 503 and expandablestructure 504 in the desired lay-flat, straightened condition. As shown,the facing ends of the tabs 510 present a nesting, serpentine geometry,which engages the catheter tube 503 essentially across its entire width,to securely retain the catheter tube 503 on the tray 508.

[0134] The kit 500 includes an inner wrap 512, which is peripherallysealed by heat or the like, to enclose the tray 508 from contact withthe outside environment. One end of the inner wrap 512 includes aconventional peal-away seal 514 (see FIG. 25), to provide quick accessto the tray 508 upon instance of use, which preferably occurs in asterile environment, such as within an operating room.

[0135] The kit 500 also includes an outer wrap 516, which is alsoperipherally sealed by heat or the like, to enclosed the inner wrap 512.One end of the outer wrap 516 includes a conventional peal-away seal 518(see FIG. 25), to provide access to the inner wrap 512, which can beremoved from the outer wrap 516 in anticipation of imminent use of theprobe 502, without compromising sterility of the probe 502 itself.

[0136] Both inner and outer wraps 512 and 516 (see FIG. 25) eachincludes a peripherally sealed top sheet 520 and bottom sheet 522. Inthe illustrated embodiment, the top sheet 520 is made of transparentplastic film, like polyethylene or MYLAR™ material, to allow visualidentification of the contents of the kit 500. The bottom sheet 522 ismade from a material that is permeable to EtO sterilization gas, e.g.,TYVEC™ plastic material (available from DuPont).

[0137] The sterile kit 500 also carries a label or insert 506, whichincludes the statement “For Single Patient Use Only” (or comparablelanguage) to affirmatively caution against reuse of the contents of thekit 500. The label 506 also preferably affirmatively instructs againstresterilization of the probe 502. The label 506 also preferablyinstructs the physician or user to dispose of the probe 502 and theentire contents of the kit 500 upon use in accordance with applicablebiological waste procedures. The presence of the probe 502 packaged inthe kit 500 verifies to the physician or user that probe 502 is sterileand has not be subjected to prior use. The physician or user is therebyassured that the expandable structure 504 meets established performanceand sterility specifications, and will have the desired configurationwhen expanded for use.

[0138] The features of the invention are set forth in the followingclaims.

We claim:
 1. A device for deployment into an interior body regioncomprising an outer catheter tube, an inner catheter tube sized andconfigured to be received within the outer catheter tube, and anexpandable structure having a distal end, a first end region adjacentthe distal end, a proximal end, and a second end region adjacent theproximal end, the distal end being bonded to the inner catheter tube toform a first bonded region and the proximal end being bonded to theouter catheter tube to form a second bonded region, the first end regionbeing inverted to overlie the first bonded region and the second endregion being inverted to overlie the second bonded region.
 2. A deviceas in claim 1 wherein inversion of the distal end of the expandablestructure creates a double-jointed distal end region.
 3. A device as inclaim 1 wherein inversion of the proximal end of the expandablestructure creates a double-jointed proximal end region.
 4. A device asin claim 1 wherein the proximal and distal ends of the expandablestructure are bonded by an adhesive bonding process.
 5. A device as inclaim 1 wherein the proximal and distal ends of the expandable structureare bonded by a melt bonding process.
 6. A device as in claim 1 whereinno portion of the inner catheter tube protrudes beyond the expandablestructure.
 7. A device as in claim 1 wherein the expandable structureprovides a maximum diameter along essentially its entire length.
 8. Amethod for manufacturing a device for deployment into an interior bodyregion comprising providing an outer catheter tube having a distal endand an inner catheter tube, the inner catheter tube being slidablewithin the outer catheter tube, providing an expandable structure havinga distal end, a first end region adjacent the distal end, a proximalend, and a second end region adjacent the proximal end, inserting theinner catheter tube into the outer catheter tube, moving the innercatheter tube a first distance beyond the distal end of the outercatheter tube, bonding the distal end of the expandable structure to theinner catheter tube to form a first bonded region, bonding the proximalend of the expandable structure to the outer catheter tube to form asecond bonded region, moving the inner catheter a second distance beyondthe distal end of the outer catheter tube, the second distance being alesser distance beyond the distal end of the outer catheter tube thanthe first distance, to invert the first and second end regions such thatthe first and second end regions overlie the first and second bondedregions respectively, and securing the relative position of the innercatheter tube and the outer catheter tube against further movement.
 9. Amethod as in claim 8 wherein the proximal and distal ends of theexpandable structure are bonded by an adhesive bonding process.
 10. Amethod as in claim 8 wherein the proximal and distal ends of theexpandable structure are bonded by a melt bonding process.
 11. A methodas in claim 8 wherein the relative position of the inner catheter tubeand the outer catheter tube are secured against further movement by anadhesive process.